JPS621827A - Recovery of metal from lead alloy - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for recovering metal from lead-metal alloys. In particular, the present invention relates to a method for recovering lead and metals, such as noble metals, from their alloys. The invention further relates to a furnace suitable for use in such a method.

In recovering precious metals such as silver and gold from primary and secondary resources, the precious metals are accompanied by lead. The lead prions that are formed are then oxidized in the molten state in a suitable container, whereby the lead is oxidized to form a liquid lead oxide slag that is slaged from the surface of the molten alloy. . Traditionally, lead oxidation has been carried out by a method known as the hebuki method. According to this method, lead prions are melted in a shallow reverberatory furnace that provides a large surface area of molten metal. The air jet impinging on the surface of the molten metal produces the required oxidation of the lead and any surge slag that forms or remains can be continuously removed to a greater or lesser extent.

Unfortunately, this conventional ash blowing method suffers from a number of drawbacks, including: (1) Necessarily high energy consumption as the molten metal is maintained at a temperature close to 1000°C; (2) Air-based The oxidation rate of the molten bath is slow; (3) a high level of skill is required on the part of the operator; (4) if the prion also contains zinc, it is often necessary to remove the zinc in the form of a viscous or surge slag; (5) refractory wear inside the furnace is relatively large at the slag/metal interface; (6) associated with airborne lead. Due to known pollution,
Requires large volumes of sanitary exhaust and process gas for cleaning at the ash blowing location.

Another method using a rotary furnace, known as a top-blown roller converter (TBRC), overcomes or at least improves on some of the problems associated with traditional blowing processes.

According to this alternative method, oxygen or oxygen-enriched air is blown through a water-cooled lance onto the molten metal as the furnace rotates. Constant furnace rotation enhances gas-solid-liquid contact, thus resulting in a greater oxidation rate than that achieved in conventional ash blowing processes.

Additionally, compared to traditional dusting processes, the TBRC process offers significant advantages in energy savings, operator skill, melting capacity, and process air pollution. Unfortunately, the UCTBRO process suffers from relatively high capital and high refractory wear due to the cleaning action of the slag.

Furthermore, the oxidation rate and oxygen availability in the TBRO process are still quite low.

1 by D.G. Norlet, B.R. Hendra and R.G.E.T. to increase the rate of shedding by improving the contact between oxygen and lead.
``The Cubulation Ope Red Copper Silver Prion'' at the Gas Sound Injection Into Liquid Metals Conference, a division of Metallurgy and Materials, Newcastle University, Tyne in April 1979. Another method was proposed in ``By Bottom Injection Op Oxydiene''. According to this method, oxygen is injected into the bottom of a deep bath instead of air being blown onto the shallow surface as in traditional ash blowing methods. Oxygen is injected through the tuyere and protected by an annular surrounding nitrogen gas.

However, the above authors report that the oxygen efficiency with this method is only about 60 degrees.

Additionally, the inventors have found that with this method, the tuyere burns severely and the refractory hearth surrounding the tuyere suffers from excessive erosion. Tuyere replacement and/or refractory lining repair are problematic in industrial scale processes. Therefore, improvements are still needed in this method.

The present inventors have found that oxygen efficiencies much lower than those reported by D.G. Barrett et al. can be achieved without suffering from the drawbacks of the method proposed by them.

The present invention melts an alloy containing lead and metals in a furnace,
Blowing a stream of oxygen-containing gas into the melt, which oxidizes the lead to form a lead oxide slag, and cooling the stream with an annular surround of coolant gas to remove the slag from the surface of the melt. A method for recovering a metal selected from precious metals and bismuth from an alloy of lead and metals comprising: a first elongated tube for an oxygen-containing gas; and a first coolant gas disposed annularly around the first tube. The oxygen-containing gas and the first coolant gas are blown into the melt through an elongated consumable lance formed from a second elongated tube for the consumable lance to pass through a lance guide tube provided in the furnace wall to the outside of the furnace. a second gas flow extending longitudinally from the exterior to the interior of the furnace, allowing the lance to be fed longitudinally from the exterior to the interior of the furnace through a guide tube as the lance is consumed in the furnace; It is characterized by blowing through the tube and sealing the lance.

In general, the method of the invention can be used for the recovery of metals selected from the group of noble metals and bismuth from alloys with lead. However, the method of the invention is particularly suitable for recovering silver from silver-lead prions. The invention will therefore be described below with reference to its application to silver recovery. one or more other non-precious metals such as antimony, arsenic, tellurium, selenium, zinc,
Copper and nickel may also be present in prions;
In this case they can be removed by volatilization or together with the oxide slag. Although there is no strict regulation on the amount of silver in prions, for economic reasons prions usually contain more than 5% silver by weight. Typically, lead prions are concentrated by conventional means.

According to the method of the invention, a stream of oxygen-containing gas is blown into the molten prion. The oxygen-containing gas is preferably oxygen itself, but mixtures of oxygen with oxygen-enriched air or with one or more other gases that are inert to the liquid metal in the bath, such as mixtures of oxygen and nitrogen, can also be used. . The reaction of lead with oxygen to form lead oxide is an exothermic reaction, and the heat produced by the oxidation reaction is absorbed by the contents of the bath.

Therefore, the method is self-generating and the actual energy consumption of this method is relatively small compared to the traditional hebuki method. However, blowing oxygen into the melt prion produces very high local temperatures at the location of oxygen blowing into the melt. To this end, the stream of oxygen-containing gas blown into the molten prion is cooled by a stream of a coolant gas, such as nitrogen or a mixture of nitrogen and methane, which is blown into the molten alloy in an annular manner around the stream of oxygen-containing gas.

The coolant gas thus provides an annular envelope around the oxygen stream. According to the invention, the oxygen-containing gas and the coolant gas are blown into the melt via an elongated consumable gas envelope lance. The lance consists of a core tube through which oxygen-containing gas is blown and an outer lance tube placed in a ring around the core tube. The coolant gas is in the melt,
It is blown through an annular opening formed by the outer wall of the core tube and the inner wall of the lance tube, thus forming an annular envelope around the blown stream of oxygen-containing gas.

During the oxidation of lead, the lance becomes consumed or burnt out, so that the lance, which extends through a guide tube located on the side or bottom wall of the furnace to a position on the exterior of the furnace, is inserted longitudinally through the tube. You can move forward. By this means, the length of the lance projecting from the refractory furnace wall into the furnace chamber can be maintained or restored.

To control the delivery of the lance to compensate for burning, the thermocouple is placed in a core tube and passed through a sealed gland to allow movement of the lance relative to the thermocouple. This thermocouple is held in a fixed position relative to the furnace and is used to sense the proximity of the lance tip as combustion occurs. When this occurs, a temperature spike is detected and this signal is used to activate a mechanical device that feeds more lances into the furnace chamber. As the lance tip moves away from the thermocouple, the temperature returns to its normal value.

The lance wear during operation of this method is actually very small;
Typically less than 4 crR/hr on average.

As mentioned above, the consumable lance used in the present invention is gas-tight, ie, it is provided with a flow of inert gas. This inert gas is blown into the furnace through a guide tube. The gas used to surround the lance need not be the same as the coolant gas used to provide an annular surround around the oxygen-containing stream, but both gases are typically nitrogen. However, in other embodiments the surrounding gas around the lance may contain or consist of a hydrocarbon gas, such as methane, since this may be advantageous in providing additional heat to the metal, especially in the final stage of the process. This is because it can be done.

Although there are no strict restrictions on the temperature of the melt in the furnace during the practice of the process of the invention, excessive operating temperatures will increase refractory wear, lance wear and smoke production. For this reason, it is preferable to control the temperature of the melt so that it does not rise to more than about 100° C. above the estimated liquidus line.

Apparently, as smelting continues, the lead content of the molten alloy decreases as the lead becomes more and more oxidized to litharge. Therefore, with a relative increase in the silver content of the alloy, the liquidus of the alloy increases until near the end of oxidation it approaches the melting point of pure silver.

Typically, the temperature of the melt during the blowing of the oxygen-containing gas is maintained at a level within the range of 50-100°C above the estimated liquidus temperature. Once the oxygen-containing gas blowing is initiated, the temperature of the melt can be substantially controlled by controlling the flow rates of the oxygen-containing gas and coolant gas from the lance.

However, towards the end of the scouring cycle, when the oxidation rate becomes too low, further heat should be supplied to the melt, for example by a conventional burner. As the lead content of the melt decreases, the oxygen requirement also decreases, so the flow rate of the oxygen-containing gas is preferably tapered towards the end of the scouring cycle. If the flow rate is not reduced, excess unreacted oxygen will cool the melt and thus lead to the formation of solid metal accretion around the edges of the lance, especially at the high melt temperatures present towards the end of the oxidation stage. .

The invention further provides a furnace suitable for use in the method of the invention, which furnace is a deep furnace of generally rectangular vertical section, which can be tilted about a fixed pivot and is equipped with at least one heater. a chamber, and at or near the top of the furnace, a means for charging the furnace and a means for discharging material from the furnace, the furnace further comprising a jet of oxygen-containing gas and a coolant gas surrounding the jet of oxygen-containing gas. A consumable lance is provided for introducing the annular envelope into the furnace, which lance extends longitudinally from the inside of the furnace to the outside through a guide tube provided in a wall, such as a side wall or a bottom wall, of the furnace. The lance guide tube extends longitudinally from the exterior to the interior of the furnace through the lance guide tube.

A preferred furnace for use in the invention will now be explained in more detail by way of example with reference to the drawings.

1 is a schematic vertical cross-section of a furnace; FIG. 2 is a schematic vertical cross-section of a preferred configuration of lances for use in the furnace shown in FIG. 1; and FIG. 4 is a schematic vertical cross-sectional view of the furnace shown in FIG. 1 in position, and FIG. 4 is a schematic vertical cross-sectional view of the furnace of FIG. 3 in reaction position;

In FIG. 1, the furnace consists of a conventional steel lining 1 with a refractory lining 2. In FIG. The furnace has a deep mold 3 of generally square vertical cross section bounded by inner walls 4, 5 and a base 6 and an openable lid 7 which can be opened for charging the furnace. The furnace has burners 8 in a recessed wall 5 to heat the contents of the furnace and a spout 9 near the top of the wall 4 to discharge slag and molten metal from the chamber when the furnace is tilted.
This is provided. A lance 10 (FIG. 2) for injecting an annular envelope of oxygen and nitrogen into the bath during operation is passed from the inside of the furnace to the outside through a guide tube 11 placed in a cast refractory zone 12 in the wall 5 near the base 6. extending itself lengthwise. Lance 10 (FIG. 2) consists of an elongated core tube 13 made of stainless steel placed within a lance tube 14 made of stainless steel. The core tube typically has an internal diameter of 4.57 m and an external diameter of 6.35 m, and the concentric annular lance tube 14 typically has an external diameter of 9.53 m and a wall thickness of 1.25 m, thus approx. .34 m wide, providing an annular gap between the inner surface of tube 14 and the outer surface of tube 13. The lance 10 is located in the lance guide tube by a sliding seal or gland 15, and a headless threaded spacer 16 is provided on the inside of the guide tube. The lance is thus sealed in the guide tube, but is slidable so that the lance can advance longitudinally through the guide tube and into the furnace chamber. This facilitates replacement of the lance when it becomes worn out during furnace operation.

Typically, in use, the lance extends approximately 4 cW1 beyond the refractory lining in the furnace. During operation, the guide tube is connected to a nitrogen gas source to provide a nitrogen surround around the lance.

The thermocouple 17 is fixed to the furnace body and placed in the lance core tube. This thermocouple is used to automatically control the lance feed, while the lance advances towards the furnace chamber but remains in place. The thermocouple is sealed at the outer end of the core tube with another ground 18.

When the lance is depleted, its hot tip is sensed by the thermocouple tip 19, which signals the motor for advancement of the lance.

This process continues until all of the lances are exhausted and a new lance can be fitted while tilting the furnace forward. Lid 7 that can be opened for silver-lead prion preparation
Add to furnace via. In the tilted position (FIG. 3), the burner 8 can be ignited to melt the prion, after which the furnace is tilted back to the reaction position (FIG. 4), so that the end of the lance 10 extends into the melt. . A stream of oxygen within a protective enclosure of nitrogen can be blown into the melt through a lance. The temperature of the molten prion during oxygen bubbling can be controlled to avoid overheating by varying the gas flow and pressure in the lance. The litharge slag formed by the oxygen-lead reaction is removed by tilting the furnace as shown in FIG. 3 until the liquid metal level matches the spout 9 and can be poured. Gas blown from the lance aids in slag removal and burner 8 is used to provide heat to maintain a free flowing slag.

The method of the present invention using the above-mentioned furnace is illustrated in the following example.

Example 1 In one furnace experiment using a consumable nitrogen-surrounded oxygen density, 65% silver, 2.2 inches of zinc, 4.0 inches of copper-lead prion 1530 was smelted to 99.8 inches of silver. did. The prion was in the form of 9 blocks of about 170 watts each. Seven blocks initially weighing 1190 Ky were placed in the furnace and melted in 90 minutes with a gas-air burner operating at an average combustion range of 8.6 thorn/hr.

The furnace is positioned at an angle to hold the lance above the liquid bath, and the gas burner is heated to 785°C, which is approximately 50°C above the metal liquidus temperature.
It was used to raise the bath temperature. During this time, the lance assembly was cooled with nitrogen at the following flow rates:

Lance guide tube: 0.15 NL/S lance enclosure: 0.15 NL/S lance core:
When the required bath temperature of 0.15 NL/S is obtained, reduce the burner to the minimum flame (1.3 therm/hr );
The following oxygen and nitrogen gas flows were set before tilting the furnace into the reaction position.

Lance guide tube: 0.3 NIJ/'S Nitrogen lance surrounding: 0.5NL/s Nitrogen lance core:
6. ONL/S Oxygen Oxygen injection is first 1.
Continued with the burner operating at low flame for 0 min, then switched as the exothermic reaction acted to maintain bath temperature above the rising liquid phase. After 25 minutes the first surge slag was removed (approximately 80 Kf) and one prion block was added to the bath. While pouring the Resurge slag, the burner was operated at a low flame that maintained a free flowing slag and the oxygen flow rate was reduced.

6. Tilt the furnace back to the reaction position and blow oxygen for 40 minutes without gas burners. This was done with ONl, /S.

The litharge was poured out again with the oxygen reduced to a minimum and the burner set to low flame (approximately 170 to 9). The last block of lead-silver prion was charged to the bath, the burner was turned off, and oxygen blowing was continued at 6 NL/S at the furnace reaction position. 15 more
After oxygen bubbling, the bath composition was evaluated at 80% silver.
The oxygen flow rate was then reduced to 5 NL/S and the burner was placed on the lowest flame. As the lead was oxidized and removed from the bath, the Lissage formation reaction slowed down, thus reducing heat production. The burner firing rate was then gradually increased and the oxygen flow rate was gradually decreased. If this is not done, excess oxygen at the lance tip will cause cooling, which will cause condensation of the silver-rich metal.

After 30 minutes, remove the Resurge slag (approximately 200V4),
Oxygen bubbling was continued at a reduced flow rate of 4 NL/S. The evaluated bath composition at this stage was 90% silver, and a bath temperature of 980°C was recorded.

After 40 minutes of oxygen blowing at 4 NL/El, litharge slag was removed again to produce 100 Ky of slag. At this stage, the bath was about 98 grams of silver and required a medium flame. Even when oxygen was blown in, no more slag was produced, so lead was added to remove copper.

Four lead charges of 75 Kq each were made and the Lissage slag layer was removed after oxygen bubbling for 30 minutes between each addition. A reduced oxygen flow rate of 3 NL/S and medium burner combustion was used during this step.

The amount of litharge removed was 350 Kg and the total amount of surge slag produced was 900 Kr.

A total of 360 minutes after the start of oxygen blowing, the silver content was 99.8%.
It was refined and ready to pour. The burner was set at a high firing rate to maintain a stable metal flow and keep the bath hot during pouring. The silver film produced was 977 cm and the total percentage of silver converted to litharge was 1.7 cm.

The total energy consumed during this experiment was 46therm, with oxygen and nitrogen consumption of 62ff/ and 20fr, respectively. Met. One entire lance was used for this furnace experiment (30 ports wasted).

Example 2 40% silver, 5% copper, 2% zinc - 1300K of lead prion
The same method described in Example 1 was used to refine f. The metal was charged again in the form of a solid block, and the bath temperature was increased to 700° C. since the metal liquid phase (approximately 620° C.) was too low to initiate the oxidation reaction. Furnace at reaction location and burner with low flame (l, 5 therm/
hr ) and oxygen was blown at 6 ML/19 for 40 minutes to generate 200 Kf litharge. As in Example 1, automatic lance feeding kept the lance tip at about 4 bacteria in the oven.

Keeping the furnace in the reaction position, the litharge slag was removed, oxygen blowing continued at 8 NL/S, and the gas burners were turned off. The energy from the exothermic oxidation of lead was sufficient to maintain the bath temperature above the elevated liquidus temperature. After an additional 30 minutes of oxygen bubbling, the oxygen was reduced and the burner was set to low flame to help remove the slag (200 mm).

Oxygen blowing was continued for another 30 minutes to remove about 200 Kp of slag. The bath composition was approximately 70% silver and the temperature was 850°C.

Further oxygen blowing at 6/30 NL/S resulted in a 150 frame surge slag and the metal bath contained approximately 90% silver. Remove the slag, use a low flame burner,
Oxidation continued at an oxygen flow rate of NL/13. After draining for 30 minutes, 80Kq of slag surge was removed, and the bath composition was approximately 97% silver.

At this point, four pieces of 75Kg of lead were added and conventional copper removal was performed. The burner was lowered to medium flame and oxygen was blown in at 3 NIJ/S. Automatic lance feeding controlled the lance to extend 4 m into the furnace.

However, during the third lead addition, the lance requires charging done with a furnace in the tilted or melting position;
It only took a few minutes.

The surge resulting from the lead addition was 330 Kf, and the total slag produced was 1160 Kg.

A total of 508 Kf of silver film was produced 390 minutes after the start of oxygen blowing. The total energy consumed is 40 ther
m, and oxygen and nitrogen consumption were 73 and 22, respectively. Silver conversion to slag was 2.3% and oxygen utilization averaged approximately 80 inches.

[Brief explanation of drawings]

1 is a schematic vertical cross-section of a furnace; FIG. 2 is a schematic vertical cross-section of a preferred configuration of lances for use in the furnace shown in FIG. 1; and FIG. 4 is a schematic vertical cross-sectional view of the furnace shown in FIG. 1 in position, and FIG. 4 is a schematic vertical cross-sectional view of the furnace of FIG. 3 in reaction position; 1-11 steel casing, 3-11 deep chamber, 7--openable lid, 8-m-burner, 9-11 spout, 10-
--Lance, 11-m-Guide tube, 13--1 single core tube, 4-m-Lance tube, 17--Thermocouple, 19--1 Thermocouple advanced procedure amendment completed July 1986 Z Day

Claims (1)

[Claims] 1. Melting the alloy in a furnace, blowing a stream of oxygen-containing gas into the melt, thereby oxidizing the lead to form a lead oxide slag, and passing the stream as a coolant gas. cooled in an annular enclosure of
A method for recovering metals selected from precious metals and bismuth from alloys containing lead and metals, comprising removing slag from the surface of the melt, the method comprising: removing slag from the surface of the melt; Blow into the melt through an elongated consumable lance formed from a first elongated tube and a second elongated tube arranged annularly around the first tube for a first coolant gas, said consumable lance being injected into the furnace wall. The lance extends longitudinally from the inside to the outside of the furnace through a provided lance guide tube and can be fed lengthwise from the outside to the inside of the furnace through the guide tube as the lance is consumed in the furnace. A method for recovering metals comprising: blowing a second gas flow through a guide tube into the furnace to seal the lance. 2. The method according to claim 1, wherein the metal to be recovered is silver. 3. The method of claim 2 for recovering silver from silver-lead prions containing at least 5% by weight of silver. 4. The method according to any one of claims 1 to 3, wherein oxygen is used as the oxygen-containing gas. 5. The method according to any one of claims 1 to 4, wherein the first coolant gas is selected from nitrogen, hydrocarbon gases and mixtures thereof. 6. The method according to any one of claims 1 to 5, wherein the second gas blown into the furnace through the lance guide tube is nitrogen. 7. The method according to any one of claims 1 to 6, in which the temperature of the melt is maintained at a value not higher than the estimated liquidus temperature of the alloy and 100° C. during the blowing of the oxygen-containing gas. 8. As the tip of the lance burns in the furnace during oxidation of lead, it is advanced longitudinally from the outside to the inside of the furnace through a guide tube by a motor located outside the furnace. The method according to any one of the ranges 1 to 7. 9. The method according to claim 8, wherein the advancement of the lance into the furnace by the motor is controlled by a thermocouple placed in the lance core tube and fixed to the furnace body. 10. A deep furnace chamber of generally rectangular vertical cross section which can be tilted about a fixed pivot, having at least one heater and having means for charging the furnace and a spout for discharging material from the furnace at or near the top of the furnace. Consisting of
The furnace is further provided with an elongated consumable lance formed from a first elongated tube and a second elongated tube disposed annularly around the first tube, the lance being inserted into the furnace through a guide tube in the wall of the furnace. 1. A furnace characterized in that it extends longitudinally from the outside to the outside so that it can be fed longitudinally from the outside to the inside of the furnace through a lance guide tube. 11. The first tube of the lance is connected to a source of oxygen-containing gas, the second tube is connected to a source of coolant gas, and the guide tube in the furnace wall is connected to the source of coolant gas.
Furnace described in item 0. 12. A furnace according to claim 10 or 11, further comprising a motor located outside the furnace for advancing the consumable lance longitudinally from the outside to the inside of the furnace. 13. The furnace according to claim 12, wherein the thermocouple is fixed to the furnace body and placed in the lance core tube, and the advancement of the lance into the furnace by the motor is controlled by the thermocouple.